Non-HLA type 1 diabetes genes modulate disease risk together with HLA-DQ and islet autoantibodies.

The possible interrelations between human leukocyte antigen (HLA)-DQ, non-HLA single-nucleotide polymorphisms (SNPs) and islet autoantibodies were investigated at clinical onset in 1-34-year-old type 1 diabetes (T1D) patients (n=305) and controls (n=203). Among the non-HLA SNPs reported by the Type 1 Diabetes Genetics Consortium, 24% were supported in this Swedish replication set including that the increased risk of minor PTPN22 allele and high-risk HLA was modified by GAD65 autoantibodies. The association between T1D and the minor AA+AC genotype in ERBB3 gene was stronger among IA-2 autoantibody-positive patients (comparison P=0.047). The association between T1D and the common insulin (AA) genotype was stronger among insulin autoantibody (IAA)-positive patients (comparison P=0.008). In contrast, the association between T1D and unidentified 26471 gene was stronger among IAA-negative (comparison P=0.049) and IA-2 autoantibody-negative (comparison P=0.052) patients. Finally, the association between IL2RA and T1D was stronger among IAA-positive than among IAA-negative patients (comparison P=0.028). These results suggest that the increased risk of T1D by non-HLA genes is often modified by both islet autoantibodies and HLA-DQ. The interactions between non-HLA genes, islet autoantibodies and HLA-DQ should be taken into account in T1D prediction studies as well as in prevention trials aimed at inducing immunological tolerance to islet autoantigens.

Attenuation of islet-specific T cell responses is associated with C-peptide improvement in autoimmune type 2 diabetes patients.

The clinical efficacy of peroxisome proliferator-activated receptor gamma (PPAR-γ) agonists in cell-mediated autoimmune diseases results from down-regulation of inflammatory cytokines and autoimmune effector cells. T cell islet autoimmunity has been demonstrated to be common in patients with phenotypic type 2 diabetes mellitus (T2DM) and islet-specific T cells (T(+) ) to be correlated positively with more severe beta cell dysfunction. We hypothesized that the beneficial effects of the PPAR-γ agonist, rosiglitazone, therapy in autoimmune T2DM patients is due, in part, to the immunosuppressive properties on the islet-specific T cell responses. Twenty-six phenotypic T2DM patients positive for T cell islet autoimmunity (T(+) ) were identified and randomized to rosiglitazone (n = 12) or glyburide (n = 14). Beta cell function, islet-specific T cell responses, interleukin (IL)-12 and interferon (IFN)-γ responses and islet autoantibodies were followed for 36 months. Patients treated with rosiglitazone demonstrated significant (P < 0·03) down-regulation of islet-specific T cell responses, although no change in response to tetanus, a significant decrease (P < 0·05) in IFN-γ production and significantly (P < 0·001) increased levels of adiponectin compared to glyburide-treated patients. Glucagon-stimulated beta cell function was observed to improve significantly (P < 0·05) in the rosiglitazone-treated T2DM patients coinciding with the down-regulation of the islet-specific T cell responses. In contrast, beta cell function in the glyburide-treated T2DM patients was observed to drop progressively throughout the study. Our results suggest that down-regulation of islet-specific T cell autoimmunity through anti-inflammatory therapy may help to improve beta cell function in autoimmune phenotypic T2DM patients.

Islet autoimmunity in phenotypic type 2 diabetes patients.

Historically, type 2 diabetes (T2D) was considered a metabolic disease of ageing. However, recent discoveries have demonstrated the role of chronic systemic inflammation in the development of insulin resistance and subsequent progression to T2D. Over the years, investigations into the pathophysiology of T2D have identified the presence of islet-specific T cells and islet autoimmune disease in T2D patients. Moreover, the cell-mediated islet autoimmunity has also been correlated with the progressive loss of ß-cell function associated with T2D disease pathogenesis. In this manuscript, the involvement of cell-mediated islet autoimmune disease in the progression of T2D disease and the similarities in islet-specific T-cell reactivity between type 1 diabetes (T1D) and T2D are discussed.

Immunology in the Clinic Review Series; focus on metabolic diseases: development of islet autoimmune disease in type 2 diabetes patients: potential sequelae of chronic inflammation.

Historically, the development of type 2 diabetes has been considered not to have an autoimmune component, in contrast to the autoimmune pathogenesis of type 1 diabetes. In this review we will discuss the accumulating data supporting the concept that islet autoreactivity and inflammation is present in type 2 diabetes pathogenesis, and the islet autoimmunity appears to be one of the factors associated with the progressive nature of the type 2 diabetes disease process.

The association between the PTPN22 1858C>T variant and type 1 diabetes depends on HLA risk and GAD65 autoantibodies.

The single nucleotide polymorphism 1858C>T in the PTPN22 gene is associated with type 1 diabetes (T1D) in several populations. Earlier reports have suggested that the association may be modified by human leukocyte antigen (HLA), as well as by islet autoantibodies. In a large case-control study of Swedish incident T1D patients and controls, 0-34 years of age, we tested whether the odds ratio (OR) measure of association was dependent on HLA or autoantibodies against the islet autoantigens glutamic acid decarboxylase 65 kDa autoantibodies (GADA), insulin, islet antigen-2, or islet cell. The association between the carrier status of 1858C>T allele in PTPN22 (PTPN22(CT+TT)) and T1D was modified by HLA. In addition, in GADA-positive T1D, the OR was 2.83 (2.00, 3.99), whereas in GADA-negative T1D, the OR was 1.41 (0.98, 2.04) (P for comparison=0.007). The OR of association between PTPN22(CT+TT) and GADA-positive T1D declined with increasing HLA-risk category from 6.12 to 1.54 (P=0.003); no such change was detected in GADA-negative T1D (P=0.722) (P for comparison=0.001). However, the absolute difference in risk between PTPN22(CC) and PTPN22(CT+TT) subjects with high-risk HLA was five times higher than that for subjects with low-risk HLA. We hypothesize that the altered T-cell function because of the PTPN22(1858C>T) polymorphism is exclusively associated with GADA-positive T1D at diagnosis.

Insulin antibodies in insulin-dependent diabetics before insulin treatment.

A sensitive assay was used to measure the binding of iodine-125-labeled insulin in serum obtained from 112 newly diagnosed insulin-dependent diabetics before insulin treatment was initiated. Two groups of nondiabetics served as controls: children with a variety of diseases other than diabetes and nondiabetic siblings of insulin-dependent diabetics. Eighteen of the diabetics were found to have elevated binding and 36 were above the 95th percentile of control values. The insulin-binding protein is precipitated by antibody to human immunoglobulin G, has a displacement curve that is parallel and over the same concentration range as serum from long-standing insulin-dependent diabetics, and elutes from a Sephacryl S-300 column at the position of gamma globulin. These insulin antibodies are present in a large percentage of newly diagnosed, untreated diabetics and may be an immune marker of B-cell damage.

Initial treatment with fixed-dose combination rosiglitazone/glimepiride in patients with previously untreated type 2 diabetes.

AIM: This study assessed the efficacy and safety of two different dosing regimens of fixed-dose combination (FDC) rosiglitazone (RSG) plus glimepiride (GLIM) compared with RSG or GLIM monotherapy in drug-naive subjects with type 2 diabetes mellitus (T2DM). METHODS: Drug-naive subjects (n = 901) were enrolled into this 28-week, double-blind, parallel-group study if their glycosylated haemoglobin A(1c) (HbA(1c)) was >7.5% but

In vivo inhibition of glucagon secretion by paracrine beta cell activity in man.

The close anatomical relationships betaeen pancreatic alpha and beta cells makes possible their interaction at a local (paracrine) level. To demonstrate this in vivo, we have compared the acute glucagon response to intravenous arginine in the basal state and after beta cell suppression by infusions of insulin. The plasma glucose concentration was maintained by the glucose clamp technique. In six normal weight nondiabetics, infusion of insulin at 0.2 mU/kg per min (rate 1) raised the mean +/- SEM plasma insulin levels from 10 +/- 3 to 32 +/- 4 mU/liter and at 1 mU/kg per min (rate 2) raised plasma insulin to 84 +/- 8 mU/liter. This resulted in beta cell suppression, as shown by a diminution in the acute insulin response (incremental area under the insulin response curve, 0-10 min): basal = 283 +/- 61, 199 +/- 66 (rate 1) and 143 +/- 48 mU/liter per 10 min (rate 2) and a fall in prestimulus C-peptide from 1.05 +/- 0.17 to 0.66 +/- 0.15 and to 0.44 +/- 0.15 mM/liter (all P less than 0.01). This beta cell suppression was associated with increased glucagon responses to arginine: 573 +/- 75 (basal), 829 +/- 114 (rate 1), and 994 +/- 136 ng/liter per 10 min (rate 2) and increased peak glucagon responses 181 +/- 11 (basal), 214 +/- 16 (rate 1), and 259 +/- 29 ng/liter (rate 2) (all P less than 0.01). In all subjects, there was a proportional change between the rise in he acute glucagon response to arginine and the fall in the prearginine C-peptide level. To demonstrate that augmented glucagon response was due to betw cell suppression, and not to the metabolic effect of infused insulin, similar studies were performed in C-peptide-negative-diabetics. Their acute glucagon response to arginine was inhibited by the insulin infusion: 701 +/- 112 (basal), 427 +/- 33 (rate 1), and 293 +/- 67 ng/liter per 10 min (rate 2) as was their peak glucagon response: 268 +/- 69, 170 +/- 36, and 115 +/- 33 ng/liter (all P less than 0.01). Thus, hyperinsulinemia, within the physiological range achieved by insulin infusion, inhibits beta cell secretion which, via a paracrine mechanism, potentiates glucagon secretion.

Major histocompatibility complex class I molecule expression is normal on peripheral blood lymphocytes from patients with insulin-dependent diabetes mellitus.

Recent work from one laboratory has shown, in both nonobese diabetic mice and humans, an association between insulin-dependent diabetes mellitus (IDDM) and quantitative difference in MHC class I molecule expression. This reported decrease in MHC class I molecule expression is very controversial in the nonobese diabetic mouse model of IDDM, but to our knowledge, it has not been evaluated by another group in human IDDM. To evaluate this question, we studied 30 patients with IDDM and 30 age- and sex-matched normal controls. MHC class I molecule expression was measured by flow cytometry with conformational-dependent MHC class I mAbs. The mean antigen density of MHC class I molecule expression in IDDM vs. normal control is 454+/-34 vs. 440+/-28 for lymphocytes and 1,440+/-117 vs. 1,494+/- 117 for monocytes, both P > 0.05. Three conformational-dependent MHC class I antibodies showed consistent results. To estimate the biological variation of MHC class I molecule expression in normal controls, we also studied 10 age- and sex-matched normal control pairs. Using X +/-SD of the percentage difference of mean antigen density in the normal control pairs as our definition of normal, we found that 70% (21/30) of IDDM patients had normal, 13% (4/30) of IDDM patients had decreased, and 17% (5/30) of IDDM patients had increased MHC class I molecule expression on lymphocytes. All IDDM patients showed normal MHC class I expression on monocytes. In conclusion, we find that there is no consistent decrease in MHC class I molecule expression on either lymphocytes or monocytes from patients with IDDM. The MHC class I molecule expression observed in IDDM patients is largely within the expected biological variation of MHC class I molecule expression that has been observed in normal controls.

Arginine-stimulated acute phase of insulin and glucagon secretion in diabetic subjects.

To determine if both phases of glucagon secretion are excessive in diabetes, arginine was admimistered intravenously as pulses and as infusions to normal subjects, insulin-dependent diabetics, and noninsulin-requiring diabetics. The acute phase of glucagon secretion, in response to arginine pulses at four different doses (submaximal to maximal alpha-cell stimulating), was indistinguishable in terms of timing, peak levels attained, and total increments comparing controls and diabetics. During the first half of the arginine infusion (500 mg/kg over 30 min) the glucagon rise in controls and diabetics was similar (P greater than 0.1), whereas during the last half of the infusion excessive glucagon levels were seen in the diabetics. No difference in the glucagon responses to arginine administered as either a pulse or an infusion was observed between the two types of diabetics. The acute phase responses of insulin to intravenous, maximal stimulating doses of glucose (20 g) and arginine (2.5 g) were measured in five insulin-independent diabetics. Although the acute insulin response to arginine was normal, there was marked attentuation of the early beta-cell response upon stimulation by glucose. From these results we conclude that although in diabetes excessive glucagon levels are observed with chronic arginine stimulation, the acute phase of glucagon secretion in response to arginine is normal. In addition, the beta-cell in noninsulin-requiring diabetics, although acutely hyporesponsive to glucose, remains normally responsive to another stimulus, arginine.

The effect of adrenergic blockade on the glucagon responses to starvation and hypoglycemia in man.

In an attempt to ascertain whether the sympathetic nervous system modulates glucagon release in man during starvation and hypoglycemia, the influence of alpha and beta adrenergic blockade on glucagon responses was studied in young, healthy men subjected to fasting and insulin-induced hypoglycemia. Six volunteers fasted for 84 h on three separate occasions. Plasma immunoreactive glucagon (IRG), measured initially at 12 h, climbed gradually from mean levels of 54 pg/ml to a zenith of 124 pg/ml at 48 h, with maintenance of these levels for the duration of the fast. The infusion of propranolol or phentolamine throughout the terminal 24 h of the second and third fasts failed to alter the pattern of IRG release. After an overnight fast, five volunteers received insulin intravenously, which evoked a mean rise in plasma IRG levels from 63 pg/ml to a maximum of 256 pg/ml at 30 min. The concurrent administration of propranolol or phentolamine did not modify the glucagon responses to insulin-induced hypoglycemia. These data suggest that the augmented glucagon release in man during starvation or after hypoglycemia is not significantly regulated by signals from the adrenergic nervous system.

Dominant inheritance of large molecular weight immunoreactive glucagon.

Plasma from some individuals contains substances which are reactive with glucagon antiserum, are larger than 3,500-dalton glucagon, and have been proposed as possible precursors of glucagon. We have evaluated three generations of a kindred in which 9 of 15 members evaluated had elevated plasma levels of large molecular weight immunoreactive glucagon (L-IRG) with an average concentration of 822 pg/ml. The distribution of individuals with elevated L-IRG levels in this pedigree is consistent with autosomal dominant inheritance. Gel filtration of plasma revealed that all affected family members had excessive amounts of two L-IRG peaks, one with a molecular weight of approximately 9,000 daltons and another in the 10,000 to 20,000-dalton range. Oral glucose tolerance tests were nondiabetic and elicited a fall in L-IRG levels, whereas L-IRG concentrations rose dramatically during the infusion of arginine. These L-IRG species may be precursors of 3,500-DALTON GLUCAGON AND MAY BE ELEVATED in this kindred because of an inherited defect in either their synthesis or degradation.

Glucagon deficiency and hyperaminoacidemia after total pancreatectomy.

The first goal of this study was to investigate whether totally pancreatectomized patients are glucagon deficient and if so, to what degree. Immunoreactive glucagon (IRG) concentrations in peripheral plasma of nine pancreatectomized patients were not significantly different from those of 10 normal controls as measured by two antisera (30-K and RCS-5) both detecting the COOH-terminal portion of the molecule and one (RCS-5) postulated to be specific for pancreatic glucagon. Plasma from six of nine pancreatectomized patients were fractionated over Sephadex G-50 and IRG was measured with both antisera in the column eluates. Using 30-K, 80.8 +/- 9% of the IRG eluted within the void volume. This material was rechromatographed on Sephadex G-200 and found to have an apparent mol wt of approximately 200,000. Only 18.3 +/- 9% eluted in the IRG3500 region. IRG3500 was significantly reduced in pancreatectomized patients as compared to normal controls (49 +/- 9 vs. 18 +/- 9 pg/ml, P less than 0.05). Using RCS-5, all IRG (corresponding to 20 +/- 6 pg/ml of plasma) eluted in the IRG3500 region. The second goal of this study was to investigate the effects of chronic glucagon deficiency on plasma amino acids. In the nine pancreatectomized patients studied, postabsorptive plasma concentrations of serine, alanine, arginine, glycine, threonine, citrulline, alpha-aminobutyrate, and tryosine were significantly elevated compared to values obtained from 20 normal controls. Physiological glucagon increments produced in two pancreatectomized patients by infusion of glucagon (6.25 and 8.0 microgram/h, respectively) resulted in normalization of the hyperaminoacidemia within 22 h. We conclude (a) that pancreatectomized patients are partially glucagon deficient because of diminished basal as well as diminished stimulated glucagon secretion; (b) that fasting concentrations of certain glucogenic amino acids are elevated in pancreatectomized patients probably as result of reduce; hepatic gluconeogenesis; and (c) that the RCS-5 antiserum is not "pancreatic glucagon" specific.

Effect of nicotinic acid-induced insulin resistance on pancreatic B cell function in normal and streptozocin-treated baboons.

To study the interaction between insulin secretion and insulin action in maintaining glucose homeostasis, we induced experimental insulin resistance in eight normal baboons, in six baboons treated with 40 mg/kg streptozocin (STZ-40), and in six baboons treated with 200 mg/kg streptozocin (STZ-200). Insulin resistance was induced by a 20-d continuous intravenous infusion of nicotinic acid (NA). Normal animals showed compensatory increases in several measures of insulin secretion (fasting insulin [FI], acute insulin response to arginine [AIRarg], acute insulin response to glucose [AIRgluc], and glucose potentiation slope [delta AIRarg/delta G]), with no net change in fasting plasma glucose (FPG) or glycosylated hemoglobin (HbAtc). STZ-40 animals showed compensatory increases in FI, AIRarg, and AIRgluc, but delta AIRarg/delta G failed to compensate. Although FPG remained normal in this group during NA infusion, HbA1c rose significantly. STZ-200 animals failed to show compensatory changes in both AIRgluc and delta AIRarg/delta G, with both HbA1c and FPG rising. These animals showed a paradoxical inhibition of insulin secretion in response to intravenous glucose during NA infusion, at a time when they were hyperglycemic. These data indicate that a significant degree of insulin resistance does not cause hyperglycemia in the presence of normal B cell function but, in animals with reduced B cell mass and superimposed insulin resistance, the degree of hyperglycemia is proportional to the degree of pancreatic B cell dysfunction.

Glucagon response to hypoglycemia in sympathectomized man.

Hypoglycemia stimulates immunoreactive glucagon (IRG) secretion and increases the activity of the sympathetic nervous system. To ascertain if the augmented alpha cell activity evoked by glucopenia is mediated by the adrenergic nervous system, the glucagon response to insulin-induced hypoglycemia of five subjects with neurologically complete cervical transections resulting from trauma, thereby disrupting their hypothalamic sympathetic outflow, was compared to six healthy volunteers. In addition to clinical neurological evaluation, completeness of sympathectomy was verified by failure to raise plasma norepinephrine levels during hypoglycemia compared to the two- and threefold increase observed in controls. Total IRG response (IRG area above basal 0-90 min) and peak IRG levels achieved were the same in the quadriplegics and the controls. Although the glucagon rise tended to be slower, and the peak levels attained occurred later in the quadriplegic patients than in the controls, this response was appropriate for their sugar decline, which was slower and reached the nadir later than in the control subjects. These observations that the glucagon release during insulin-induced hypoglycemia is normal in subjects whose hypothalamic sympathetic outflow has been interrupted provide strong evidence that the sympathetic nervous system does not mediate the glucagon response to hypoglycemia.

Prediction and prevention of IDDM--1991.

Although we can now identify some nondiabetic individuals who will subsequently develop clinical insulin-dependent diabetes mellitus (IDDM), our ability to predict subsequent clinical IDDM is far from perfect. In this article, we discuss the status of knowledge regarding the natural history of preclinical IDDM and discuss, especially in relation to predicting IDDM, the genetic, immunologic, and metabolic components of the IDDM disease process.

Stimulation of glucagon secretion by ethanol-induced hypoglycemia in man.

In fasted man, ethanol lowers plasma glucose by inhibiting gluconeogenesis with concomitant suppression of insulin release. Since glucose regulation of glucagon (IRG) secretion may be insulin dependent, we have evaluated IRG secretion in this setting of hypoglycemia and insulin deficiency. Mean IRG levels in six men fasted for fifty-six hours rose gradually from a basal level of 57 pg/ml. to 101 pg/ml. During the subsequent four-hour ethanol infusion, mean glucose concentration fell only 18 mg. per 100 ml. (26 per cent of pre-infusion values) yet IRG tripled to 265 pg/ml. Insulin (IRI) fell to unmeasurably low values. Alcohol given after only eight hours of fasting has no effect on plasma levels of glucose, IRG and IRI. These results suggest that the small decrease in extracellular glucose combined with relative insulin deficiency may cause inordinate intra-alpha cell glucopenia and result in exaggerated glucagon release.

Immunoreactive glucagon responses to oral glucose, insulin infusion and deprivation, and somatostatin in pancreatectomized man.

In a group of pancreatectomized subjects, immunoreactive glucagon (IRG) concentrations were normal after an overnight fast, increased after oral glucose, were not suppressed by somatostatin (SRIF) or insulin, and in two of four subjects they rose with an arginine infusion. Even though the SRIF infusion failed to lower IRG, there was a fall in plasma glucose concentration in both subjects. In two subjects, endogenous hyperglycemia occurred during insulin withdrawal without a rise in IRG, and, in one subject, mild diabetic ketoacidosis developed with only a minimal rise in IRG. These results support the presence of an extrapancreatic source of IRG in man. Secretion from these extrapancreatic alpha cells appears to be regulated differently than secretion from pancreatic alpha cells.

Repair of pancreatic beta-cells. A relevant phenomenon in early IDDM?

Most studies dealing with the pathogenesis of IDDM have emphasized the immune assault against beta-cells. In this perspective, we review the data that suggest that the beta-cell destruction of IDDM depends on a balance between beta-cell damage and repair. The progressive beta-cell damage leading to IDDM seems to follow markedly different temporal courses in individual patients. Some individuals at high risk for developing IDDM, and presenting with impaired beta-cell function, appear to recover beta-cell function when followed prospectively. Moreover, after the clinical onset of IDDM, most patients experience a transitory period of improved insulin secretion. In vitro and in vivo experimental data suggest that beta-cells are indeed able to repair themselves after damage. Dispersed beta-cells or whole islets can survive and regain their function after a toxic assault. Furthermore, the abnormal insulin release and glucose oxidation of islets isolated from NOD mice during the prediabetic period is completely restored after 1 wk in tissue culture. Finally, treatment of NOD mice with monoclonal antibodies directed against infiltrating T-cells reverses the altered glucose metabolism of beta-cells. Note that beta-cell repair after exposure to different toxic agents can be enhanced both in vivo and in vitro. Potential enhancers of beta-cell repair are nicotinamide, glucose, protein-rich diets, and branched chain amino acids. A basic question that remains to be answered is the nature of the repair mechanisms triggered by beta-cells.(ABSTRACT TRUNCATED AT 250 WORDS)